Adaptive direct pressure shift control for a motor vehicle transmission

Abstract

An adaptive shift control system for regulating the operation of a fluid operated torque establishing device associated with a specified speed ratio in a motor vehicle automatic transmission. Shifting from a currently engaged speed ratio to the specified speed ratio includes a preparation phase during which fluid is supplied to the torque establishing device for a predetermined time to fill the same in preparation for torque transmission, and a completion phase during which further fluid is supplied to the device to initiate and progressively increase the transmission of torque therethrough. The change in transmission input speed due to the initiation of torque transmission through the torque establishing device is identified and used to detect the occurrence of overfill or underfill conditions. The predetermined time is adjusted based on such detection so as to adaptively compensate for sources of error which degrade the shift quality by causing overfill or underfill conditions.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follow: 
     
       1. In a shift control system for a motor vehicle multiple speed ratio automatic transmission having a fluid operated torque establishing device associated with a specified speed ratio and a source of fluid pressure, wherein shifting from a currently engaged speed ratio to said specified speed ratio includes a preparation phase during which fluid is supplied from said source to the torque establishing device for a predetermined time to fill the same in preparation for torque transmission, and a completion phase during which further fluid is supplied to the torque establishing device to initiate and progressively increase the transmission of torque therethrough, a method of adaptively correcting the predetermined time for sources of error which degrade the shift quality by causing an overfill condition wherein the initiation of torque transmission through the torque establishing device occurs prior to the commencement of the completion phase or an underfill condition wherein the initiation of torque transmission through the torque establishing device occurs after the commencement of the completion phase, said method comprising the steps of: detecting the occurrence of a change in transmission input speed due to the initiation of torque transmission through said torque establishing device;   developing an actual time indication in relation to the detected occurrence of input speed change and a reference time indication in relation to the time at which an input speed change would be expected to occur during normal operation;   comparing the actual time indication to the reference time indication in order to detect the occurrence of overfill or underfill conditions; and   adjusting said predetermined time in accordance with said comparison so as to increase the predetermined time when an underfill condition is detected, and decrease the predetermined time when an overfill condition is detected, thereby to improve the shift quality in subsequent shifts to said specified speed ratio.   
     
     
       2. The method set forth in claim 1, including the step of: determining the amount of adjustment of said predetermined time in accordance with a first term dependent on the difference between said actual and reference time indications and a second term dependent on the integral of such difference with respect to time.   
     
     
       3. The method set forth in claim 2, including the step of: resetting said second term to zero when the difference between said actual and reference time indications changes sign and has a magnitude in excess of a reference amount.   
     
     
       4. The method set forth in claim 2, including the step of: limiting the amount of adjustment of said predetermined time to a maximum reference determined in relation to the difference between said actual and reference time indications.   
     
     
       5. The method as set forth in claim 1, including the steps of: delaying the adjustment of said predetermined time substantially until the end of the completion phase of said shift; and   detecting a condition of an abnormal rate of torque transmission through the torque establishing device in the completion phase of the speed ratio shift which could alter the detected occurrence of input speed change used to develop said actual time indication; and   limiting the adjustment of said predetermined time to a relatively small amount in response to such detection so as to prevent substantial adjustment of said predetermined time following shifts wherein an abnormality in the completion phase thereof could result in an erroneous detection of overfill or underfill condition.   
     
     
       6. The method set forth in claim 1, including the steps of: identifying the occurrences of substantial deviation between the actual and reference time indications in at least one direction; and   limiting the adjustment of said predetermined time in response to such occurrences to a relatively small amount until such occurrences have been identified in a predetermined number of successive shifts involving the torque establishing device.   
     
     
       7. The method set forth in claim 1, including the steps of: identifying vehicle operating conditions for which the occurrence of an overfill condition cannot be reliably detected; and   in response to the identification of such operating conditions, permitting adjustments which increase the predetermined time if a relatively large underfill is detected, and otherwise decreasing the predetermined time by a relatively small reference amount, whereby if the decrease degrades the shift quality, an underfill condition will be detected in subsequent shifts involving the torque establishing device, and such decreasing of the predetermined time will be reversed.   
     
     
       8. In a shift control system for a motor vehicle multiple speed ratio automatic transmission having a fluid operated torque establishing device associated with a specified speed ratio and a source of fluid pressure controlled to develop fluid pressure in accordance with a line pressure command, wherein shifting from a currently engaged speed ratio to said specified speed ratio includes a preparation phase during which fluid is supplied from said source to the device for fill interval to fill the device in preparation for torque transmission, and a completion phase during which further fluid is supplied to the device to initiate the transmission of torque therethrough, a method of compensating for sources of error which degrade the shift quality by causing an overfill condition wherein the initiation of torque transmission through the torque establishing device occurs prior to the commencement of the completion phase or an underfill condition wherein the initiation of torque transmission through the torque establishing device occurs after the commencement of the completion phase, said method comprising the steps of: determining the fill interval as a stored function of the line pressure command;   detecting the occurrence of a change in transmission input speed due to the initiation of torque transmission through said torque establishing device;   developing an actual time indication in relation to the detected occurrence of input speed change and a reference time indication in relation to the time at which an input speed change would be expected to occur during normal operation;   comparing the actual time indication to the reference time indication in order to detect the occurrence of overfill or underfill conditions; and   adjusting said stored function in accordance with said comparison so that if an underfill condition is detected, the fill interval determined in subsequent shifts to said specified speed ratio will be longer than would otherwise occur and so that if an overfill condition is detected, the fill interval determined in subsequent shifts to the specified speed ratio will be shorter than would otherwise occur, thereby to improve the shift quality such subsequent shifts.   
     
     
       9. In a shift control system for a multiple speed ratio automatic transmission having a fluid operated torque establishing device associated with a specified speed ratio and a source of fluid pressure, wherein shifting from a currently engaged speed ratio to said specified speed ratio includes a preparation phase during which fluid is supplied from said source to the device for predetermined time to fill the device in preparation for torque transmission, and a completion phase during which further fluid is supplied to the device to initiate the transmission of torque therethrough, a method of adaptively correcting the predetermined time for sources of error which degrade the shift quality by causing the torque establishing device to be overfilled or underfilled at the end of the preparation phase, said method comprising the steps of: sampling information related to the transmission input speed during the course of the speed ratio shift;   predicting a future transmission input speed value based on an extrapolation of previously sampled transmission input speed related information;   indicating a detection of transmission input speed change due to the initiation of torque transmission through the torque establishing device when the current transmission input speed differs from the predicted transmission input speed by at least a reference amount;   developing an actual time indication in relation to the detected occurrence of input speed change and a reference time indication in relation to the time at which an input speed change would be expected to occur in normal operation;   comparing the actual time indication to the reference time indication in order to detect the occurrence of overfill or underfill conditions; and   adjusting said predetermined time in accordance with said comparison so as to increase the predetermined time when an underfill condition is detected, and decrease the predetermined time when an overfill condition is detected, thereby to improve the shift quality in subsequent shifts to said specified speed ratio.   
     
     
       10. The method set forth in claim 9, including the steps of: defining a window of time in relation to the end of said predetermined time such that in worst case underfill and overfill conditions, the change in transmission input speed due to the initiation of torque transmission through the torque establishing device would occur within the window; and   enabling the detection of overfill and underfill conditions only within said window, thereby to minimize the likelihood of erroneously adjusting said predetermined time due to the presence of spurious noise in the sampled speed related information.   
     
     
       11. The method set forth in claim 9, including the steps of: filtering the actual speed error values to provide a measure of the spurious noise present in the transmission input speed related information; and   adjusting the reference error value in relation to said measure of spurious noise, thereby to minimize the likelihood of erroneously adjusting said predetermined time due to the presence of spurious noise in the sampled transmission input speed related information.   
     
     
       12. In a shift control system for a multiple speed ratio automatic transmission having a fluid operated torque establishing device associated with a specified speed ratio and a source of fluid pressure, wherein shifting from a currently engaged speed ratio to said specified speed ratio includes a preparation phase during which fluid is supplied from said source to the device for a predetermined time to fill the device in preparation for torque transmission, and a completion phase during which further fluid is supplied to the device to initiate the transmission of torque therethrough, a method of adaptively correcting the predetermined time for sources of error which degrade the shift quality by causing the torque establishing device to be overfilled or underfilled at the end of the preparation phase, said method comprising the steps of: initiating the measurement of a time interval at the commencement of the preparation phase of said shift;   predicting a future transmission input speed value based on an extrapolation of current and previously sampled information relating to the transmission input speed;   developing an actual speed error value in relation to the difference between the current transmission input speed and the predicted transmission input speed;   sampling the measured time interval when the actual speed error value exceeds a reference error value to obtain a measure of the time required to effect an input speed change due to the initiation of torque transmission through said torque establishing device;   comparing the sampled time interval with a reference interval representative of the time that would normally be required for the initiation of torque transmission through the torque establishing device to effect a transmission input speed change, to thereby detect the occurrence of an overfill or underfill condition; and   adjusting said predetermined time in accordance with said comparison so as to increase the predetermined time if an underfill condition is detected, and decrease the predetermined time if an overfill condition is detected, thereby to improve the shift quality in subsequent shifts to said specified speed ratio.   
     
     
       13. In a shift control system for a multiple speed ratio automatic transmission having a fluid operated torque establishing device associated with a specified speed ratio and a source of fluid pressure, wherein shifting from a currently engaged speed ratio to said specified speed ratio includes a preparation phase during which fluid is supplied from said source to the device for a predetermined time to fill the device in preparation for torque transmission, and a completion phase during which further fluid is supplied to the device to initiate the transmission of torque therethrough, a method of adaptively correcting the predetermined time for sources of error which degrade the shift quality by causing the torque establishing device to be overfilled or underfilled at the end of the preparation phase, said method comprising the steps of: initiating the measurement of a time interval at the commencement of the preparation phase of said shift;   predicting a future transmission input speed value based on an extrapolation of current and previously sampled information relating to the transmission input speed;   developing an actual speed error value in relation to the difference between the current transmission input speed and the predicted transmission input speed and;   sampling the measured time interval when the actual speed error value exceeds a first relatively low reference error value, and thereafter retaining the sampled interval as a measure of the time required to effect an input speed change due to the initiation of torque transmission through said torque establishing device only if the actual speed error subsequently exceeds a second relatively high error value, whereby the sampled time interval is only retained if the occurrence of a change in transmission input speed is subsequently verified;   comparing the retained time interval sample with a reference interval representative of the time that would normally be required for the initiation of torque transmission through the torque establishing device to effect a transmission input speed change, to thereby detect the occurrence of an overfill or underfill condition; and   adjusting said predetermined time in accordance with said comparison so as to increase the predetermined time if an underfill condition is detected, and decrease the predetermined time if an overfill condition is detected, thereby to improve the shift quality in subsequent shifts to said specified speed ratio.   
     
     
       14. The method set forth in claim 13, including the steps of: filtering the actual speed error values to provide a measure of the spurious noise present in the transmission input speed related information; and   adjusting the first and second reference error values in relation to the said measure of spurious noise, thereby to to minimize the likelihood of erroneously adjusting said predetermined time due to the presence of spurious noise in the sampled speed related information.